a. Field of Invention
The invention relates generally to vehicle door latch release systems, and, more particularly, to a vehicle passive entry side door latch release system that can operate with existing door latch assemblies.
b. Description of Related Art
In recent years, automatic vehicle door latch release systems have become increasingly popular and are now available in a variety of new vehicles. Such door latch release systems normally operate by sending an electrical signal to a latch release unit when an operator either pulls an outside door handle, depresses an actuation switch underneath or adjacent the handle, or otherwise approaches the vehicle with a remote access unit. Once the outside handle is pulled or otherwise actuated, the latch release unit must release the latch or otherwise unlock the door within 50 ms or less to enable seamless operation of the latch release (or unlocking) and door opening functions.
More specifically, the operation of a typical passive latch release system is initiated when a user carrying a remote transmitter (i.e. a key fob) approaches a vehicle. The latch release system is thus activated upon the user's approach and verifies an encoded signal sent by the remote transmitter to activate the system. The latch release system then authenticates the encoded signal and performs a series of functions for allowing the user to open the door.
Such an exemplary passive latch release system is disclosed for example in U.S. patent application No. 2004/0195845 to Chevalier. Referring to FIGS. 1-3 of Chevalier, the latch arrangement (100) includes an electric motor (34) controlled by an electronic control unit (7) and further includes a plurality of actuators (700, 800) arranged to release, lock and/or unlock the latch to a vehicle door. The electronic control unit (7), which controls motor (34) to release, lock and/or unlock the latch, is responsive to movement of an external manual actuator for allowing the door to be opened. Another exemplary passive latch or lock release system is disclosed in U.S. Pat. No. 6,474,704 to Rathmann. Referring to FIG. 1 of Rathmann, the latch release system includes two actuating motors (10, 13) to drive multiple step down gears (15, 16, 8) to rotatably displace a latch pawl (4).
Latch release systems, such as the systems disclosed by Chevalier and Rathmann, as well as other U.S. Patents and Publications such as U.S. Pat. No. 6,367,296 to Dupont and U.S. Publication No. 2005/0134953 to Spurr, thus require a relatively complex latch release assembly for actuating a door latch via the outside door handle or otherwise via a remote unit. However, for existing conventional latch release systems which generally include an outside door handle and latch rod assembly for operating a door latch from the outside of a vehicle, and an inside door handle and release cable assembly for operating the door latch from the inside of a vehicle, the noted Chevalier passive latch release system is inoperable without removal and replacement of the existing latch release assembly. While such removal and replacement of the existing latch release assembly may be performed on a limited basis, it would be beneficial to have a door latch release system which is operable with existing latch release assemblies while minimizing the time and expense of modifying or otherwise replacing an existing assembly for automatic latch release operation. While the Rathmann passive latch release system decreases current demand for operation, this is at the expense of operation speed and component complexity. Other systems, while able to operate a door latch within 50 ms, require motors with high space and current demands that are difficult to meet in vehicle applications.
Accordingly, there remains a need for a door latch release assembly, which is economical to manufacture, install and service, in vehicles with existing conventional latch release assembly designs, as well as in vehicles where the latch release or door unlock assembly is operable by pulling one or more release cables. There also remains a need for a door latch release assembly which is robust in design for long term use in a variety of vehicles, which reduces design and tooling costs, and which further meets automotive fit and operation requirements for such components. Additionally, there remains a need for a latch assembly that consumes a low amount of current yet can actuate a latch in a short period of time, while minimizing overall component package space.